In complementary bipolar complementary-metal-oxide semiconductor (BiCMOS) fabrication processes, bipolar devices and CMOS devices are integrated on the same semiconductor substrate. High performance bipolar devices, such as NPN and PNP silicon-germanium (SiGe) bipolar transistors, require a high mask count when integrated on the same semiconductor substrate as the CMOS devices. As BiCMOS technology continues to advance in an effort to achieve high performance, such as increased speed, frequency response and gain, and reduced power consumption, semiconductor manufacturers are challenged to provide a complementary BiCMOS process that effectively integrates higher performing bipolar and CMOS devices.
In one approach of complementary BiCMOS process flow, when forming a bipolar device (e.g., a PNP device), a collector of the bipolar device is formed, for example, by implanting a P type dopant. Consequently, at least one masking layer is required to form the collector when implanting the P type dopant. Thereafter, an insulating layer is formed over the collector of the bipolar device. To form a base for the bipolar device over the collector, a window opening needs to be formed by, for example, etching away a portion of the insulating layer above the collector. Thus, another masking layer is required over the insulating layer to form the window opening for the deposition of the base layer. A similar process is used to form the other bipolar device (e.g., an NPN device) during the complementary BiCMOS process flow. Thus, the formations of the bases and the collectors for the complementary bipolar devices require separate implanting steps and a number of masking layers. These steps in the complementary BiCMOS process undesirably add to processing complexity and manufacturing cost.
Thus, there is a need in the art for a complementary BiCMOS process for efficiently integrating complementary bipolar devices, such as SiGe NPN and PNP devices, with CMOS devices without undesirably increasing processing complexity and manufacturing cost.